Removing printing ink from paper



-p...a. oa6,1'931' UNITED STATES PATENT orrlca mm B. KINYON AND BEIGE KINYON, OF SOUTH BEND, INDIANA;

REMOVING- PBINTING INK FROM IPAJPEB Io Drawing.

The present invention relates to a process for removing printing ink from paper for the purpose of producing a pulp which may be reworked into new pa er or be incorporat- 5 ed with fresh paper stoc in the-manufacture of aper and cardboard.

ne of the objects of the invention is" to separate the ink from printed paper by a 've simple and economical method which di ers from that of theprior art by using only a single reagent and which can therefore be carried out at a minimum of expense and in a comparatively simple apparatus. Another object of the invention is to treat 7 p ted paper with a solution of soap containing no added free alkali.

- Another object of the invention is to treat printed paper with a solution of naphtha soa (Ither objects of the invention will appear in connection with the description and claims herein below.

It has already been proposed to remove ink from paper by means of solutions containing ink so as to allow of the suspension of the pigment of the ink in water for its eventual separation from the fibre. For example, it has been proposed to treat paper with organic solvents, such as kerosene, turpentine, gasoline, benzine and the like, in conjunction with alkalis such as soda ash and soap. Combinations of soaps with organic water soluble colloids, such as glucose, and other sugars, -have also been proposed.

The use of water-insoluble soaps, such as calcium and magnesia soaps, which are dissolved in an organic liquid, as kerosene, such as can be mixed with water to form an emulsion of the water-in-oil type has been patent ed, but, obviously, is an expensive reagent, as it requires the separation and removal of a valuable organic solvent in order to make the process commercially feasible.

The present process differs from all of the preceding processes, they being predicated upon a comparatively simple reagent, namely, naphtha soap. The novelty in the present method resides mainly in the fact that the reagents capable of loosening, dissolving or distintegrating the binder or vehicle of the Application filed July 23, 1930. Serial No. 470,241.

carbon in the ink is wet by the naphtha in the soap, while the cellulosic fibers are referentially wetted by the water, thus Ina 'ng the carbon particles repellant to the cellulose, so that when they are once loosened they will not again adhere to the cellulose.

however, the cellulose of which the paper is made will be attacked, the alkali combining with the paper to form a compound of the type of soda-cellulose. This takes place even though the solution is fairly dilute, although the compound is very labile and readily dc composed on subsequent washing. In the presence of alkalies there is also a slight hydration of the cellulose which renders the same very adsorbent to any colloidally dispersed particles, whereby the said particles will become redeposited uniformly upon the cellulose fibres, and hence impossible to remove their association with the fibre.

It is obvious that uniess the cellulose is maintained in as nonadsorbent condition as possible, a real separation of the ink from the paper is impossible.

c This has been the eat ditflculty with all of the processes of t e past, which, at best, merely loosened the ink from the paper where it had been distributed in definite areas corresponding to the print or pictures, and thereafter dispersed the ink uniformly throughout the pulped paper with the resultant darkening of, the pulp, which was gray and unsightly, and whichno amount of bleaching could whiten. In other words, what resulted was a uniform dispersion of the carbon of the printing ink among the fibers of the paper.

tially wetted by the naphtha in the soap, and

, not rendered adsorbent thereof, so that when, l

' paper-making art.

hence is .held in suspension, but the paper is after agitating the mixture of paper and soapy water to separate the fibers, the mixture is filtered, the suspended pigment and vehicle will pass through the screen, -while' the fibers remain behind. A simple washing then makes it possible to remove the rest of the ink from the paper, leaving a much whiter pulp than has ever been prepared before by any method described in the prior art.

In carrying out the process, a solution of approximately the strength of one'oiince of commercial naphtha soap in from seven to twelve gallons of water is employed. It is advisable to use softened water so as to avoid the formation of'wa'ter insoluble lime and magnesia soaps, as these interfere with the proper separation of the loosened ink from the fiber. The solution should foam freely, but should not contain any appreciable amount of free alkali, preferably having a hydrogen-ion concentration of about plil 8.4-8.7.

The paper is immersed in this'solution' of soap and beaten therein at a temperatureof from 110F. to 180 F. so as to disintegrate the same into a loose pulp-like mass. The temperature dependson the kind of paper used, as more particularly pointed out hereinbelow. During this beating the ink will become loosened from the paper and will disperse itself in the soapy solution. The presence of the naphtha in the soap does not interfere with this action, but helps the action as far as'the loosening of the ink is concerned. The naphtha has a tendency to wetthe carbon particles, thereby rendering them very slightlyfrepellant to the cellulosic fibers which arewetted by the water, as a result of which a redeposition of the suspended carbon particles upon' the paper pulp is prevented. I v

The temperatureat which the process is carried out varies somewhat. For example,-

with ground-wood stock, from 110 F. to 120 F. suflice, as this stock readily goes back into fibrous form, and also readily releases the ink'from the paper made withit. For sulfite stock papers the temperature most satisfactory lies between 140 F. and 150 F. For heavy coated magazine stock, which is usually also loaded with fillers, the temperature required may be as high 'as 180 F. but actual boiling of the paper with the soap solution is to be avoided.

, The process may be carried out in any of the available machinery employed in the The main desideratum is the breaking up of the binder in the ink, the suspension of the carbon particles in the soap solution, and the pulpin of the paper so as to break it up into indivi ual fibers that float freely about the solution. The solution containing the suspended paper and carbon particles is then'filtered in any suitable manner, through a screen that while fine enough to retain substantially all of the fibers will freely pass the suspension of carbon particles. The paper pulp is preferably given one thorough washing, either with softened or with ordinary water. It may, if very heavily inked, be desirable to suspend the filtered pulp in a fresh quantity of water and again to filter it, but in most instances mere washing on the filter is suflicient.

The de-inking process of our present invention is well adapted to the continuous process used-in paper mills, as the pulp may also be washed free of carbon particles in suspension in the soap solution by the aid of a Decker washer. The pulp may, if necessary, be removed from the solution and be washed in a fresh soap solution, or in water, in the said washer, the solution obtained (when soap is used for the second washing) being subsequently employed for the first washing or die-inking of a fresh batch of paper. The pulp in any case is finally washed with clear water.

A gbod pulp, free from carbon, is produced, and "this may then be treated in any manner as conditions may warrant. It may be .sheeted," orv mixed with other pulp, or utilized in any desired manner. Bleaching is usually not required, but a small amount of acid, when added to the final rinse of the de-inked stock, will somewhat brighten its color. The time required to work up a batch of paper is about one hour. The paper may be somewhat comminuted before being subjected to the soap bath, though usually the agitation of the bath will suffice to comminute the paper to the desire degree.

The solution containing the soap and carbonis of no particular value, but if it is desired to recover the carbon, this can readily be accomplished by treating the solution with an acid so as to decompose the soap; thereafter the particles will agglomerate and can either be filtered from the solution, or re- -moved by centrifugal means. This, however,

part of the present invenreserve proximately the equivalent of one ounce of soap in from seven to twelve gallons of soft water.

It is to be distinctly understood that the. entire operation is carried out in a practically neutral solution, and that no other reagents, such as alkalies, calcium hypochlorite,

and the like, are employed; this feature characterizing the present invention and distin- I guishing the same from the hitherto proposed processes for de-inking paper.

What it is desired to protect by Letters Patent of the United States is:

1. The process of removing printing ink from paper which comprises subjecting said paper to the action of a solution of naphtha soap in soft water whereby the ink is loosened from the paper and removable from the resulting paper pulp by simple filtration of said pulp, the carbon particles from the ink passing through with the filtrate.

2. The process of removing printing ink from paper which comprises agitating said paper in a warmsolution of naphtha. soap in soft water until a pulp of paper and liberated carbon particles from the ink is obtained, straining said pulp whereby the liberated carbon particles are separated from the cellulosic fibersof the pulp, and washing said pulp substantially free from soap solution.

3. The process of removing printing ink "from paper which comprises agitating said 'cles but fine enough to retain and filtering said paper fibers from the finer carbon particles.

6. The process of removing printing ink from paper which, comprises loosening the ink from said paper by means of a solution of naphtha soap and water, said solution having'a hydrogenion concentration not over pH 8.9, and separating the loosened ink from the fibers of the paper by filtration.

7. The process of removing printing ink from paper which comprises agitating comminuted printed paper in a solution of a water-soluble soap containing naphtha and which solution has a hydrogen-ion concentration between pH 8.4 and pH 8.7 at a temperature between 120 and 180 F., until a suspension of the paper fibers and carbon particles from the printingl ink is formed, filtering said suspension t rough a screen fine enough freely to pass the carbon partisubstantially all of the paper fibers, and washing said separated paper 'fibers.

In witness whereof, we have hereunto subscribed our names.

' MINNIE E. KINYON.

BRICE W. KINYON.

paper in a solution of naphtha soap in warm water at temperatures-between 120 F. and 180 F to loosen the ink and to distribute the carbon particles thereof throughout the soap solution, and subsequently filtering the resulting paper pulp to separate the said carborl particles from the cellulosic fibers of the u p. p 4. The process of removing printing ink from paper which comprises comminuting the paper, placing it into a warm solution of naphtha soap in water and agitating it therein until the 'paper has become converted into a pulp and the ink resolved into dissolved ink vehicle and free carbon particles which ,re-

main suspended in the mixture of pulp and soap solution, and filtering said solution through a screen fine enough to retain the paper particles but coarse enough to pass freely the carbon particles.

5. The process of preventing the re-ad herence of carbon particles derived from resolved printing ink upon suspended paper fibers, whichecomprises treating said paper fiberswitha naphtha soap, whereby the na'phtha preferentially wets the carbon particles while the water wets the cellulosic fibers of the paper whereby re'deposition of the carbon particles on the paper fibers is prevented; 

